diff --git a/cmd/clitest/main.go b/cmd/clitest/main.go
index ddc67d5..ca799d1 100644
--- a/cmd/clitest/main.go
+++ b/cmd/clitest/main.go
@@ -82,6 +82,27 @@ func main() {
 
 			// MODIFIERS
 			if predictionMonths, err := strconv.ParseInt(r.URL.Query().Get("predictionMonths"), 10, 16); err == nil && predictionMonths > 0 {
+				for _, whatIf := range r.URL.Query()["predictWhatIf"] { // ?whatIf=2023-01=AssetAccount:Cash=$=-1.00
+					date := strings.Split(whatIf, "=")[0]
+					name := strings.Split(whatIf, "=")[1]
+					currency := ledger.Currency(strings.Split(whatIf, "=")[2])
+					delta, err := strconv.ParseFloat(strings.Split(whatIf, "=")[3], 64)
+					if err != nil {
+						panic(err)
+					}
+					mostRecentDateBefore := ""
+					for _, d := range register.Dates() {
+						if _, ok := register[d][name]; !ok {
+							continue
+						} else if d > date {
+							continue
+						}
+						mostRecentDateBefore = d
+					}
+					balanceWouldBe := maps.Clone(register[mostRecentDateBefore][name])
+					balanceWouldBe[currency] += delta
+					register[date][name] = balanceWouldBe
+				}
 				predictionDuration := time.Hour * 24 * 365 / 12 * time.Duration(predictionMonths)
 				if r.URL.Query().Get("predictContributions") != "" {
 					register, err = ledger.RegisterWithContributionPrediction(register, predictionDuration)